Race Day Nutrition: How Your 50K Fueling Plan Should Change Based on the Race You Choose
- Justin Biays
- May 9
- 7 min read
Not all 50Ks are built the same — so your fueling plan shouldn’t be either.
The kind of race you choose dictates everything about race day: how fast you go, how long you’re out there, how much you’ll sweat, and what your stomach can handle. If you think you can take the same plan to a flat road race and a 9-hour mountain sufferfest, you’re going to have a bad time.
This is where most new ultra runners blow it. They train smart, eat well in the lead-up, and then race day hits — and their fueling plan doesn’t match the course.
We’re going to fix that.
Below, you’ll find how race type changes your nutrition plan, what to expect, and how to prep like a pro.
While we recommend reading the whole post, you can jump to specific sections here:
Road 50K: Predictable Pace, Precision Fueling
Road ultras are the most straightforward terrain-wise, but they come with their own challenges — mainly pace and digestion. Since you’re running continuously- and at a fairly steady effort- you have the benefit of predictable timing for fueling. But, you also have less downtime and fewer “breaks” to adjust or recover from poor choices.
Overall, you won’t be walking much, which means your stomach will be bouncing the entire time. This means smooth and simple is going to be key. Fuel has to be light, fast-digesting, and easy to consume without interrupting your rhythm.
Duration Expectation: Most well-trained athletes will finish a road 50K in 4–6 hours.
Pacing: You’ll be running at a steady, moderate pace with little walking. That means less opportunity to “pause” for nutrition or adjust mid-effort.
What Works Best: Stick with carb-based fuels that require no chewing and minimal digestion. Gels, drink mixes, and chews are ideal here. Think speed and simplicity.
Fuel Timing: Aim to consume 30–60 grams of carbohydrate every 30–40 minutes. Time it based on minutes, not miles, since the terrain won’t change much.
Hydration Strategy: Aid stations will likely be every 2–4 miles. You can rely on them more than in trail races, but you should still carry a small handheld or bottle. Sipping small amounts frequently helps digestion and pacing.
Common Pitfall: Overeating or choosing complex foods that sit in your stomach too long. Remember, you’re running fast — your gut won’t like that burrito you thought was a good idea at mile 20.
Practice your race-day fueling in your long tempo runs. If your stomach can’t handle your fuel at training pace, it won’t magically work on race day.
Trail 50K: Varied Terrain, Flexible Strategy
Trail 50Ks introduce more terrain changes and pacing variability than road races. Expect to switch between running, hiking, and power hiking frequently, especially on climbs and descents.
This gives you more opportunities to fuel during lower-intensity sections — but also more opportunity to forget or mistime your fuel if you don’t have a solid plan.
Duration Expectation: Expect 5–7+ hours of total race time depending on the course and elevation gain.
Pacing: You’ll slow down on climbs, speed up on descents, and mix hiking with running based on terrain. This opens up windows to fuel more comfortably.
What Works Best: A combination of gels, chews, and real food like bananas, nut butter packs, rice balls, or PB&Js. Mix it up to avoid gut fatigue.
Fuel Timing: Stick with a “time-based” plan — consume 30–60g of carbs every 40–50 minutes. Your pace will vary too much to base it on distance.
Hydration Strategy: Trail races usually have more spaced-out aid stations (every 5–8 miles), so plan to carry your own fluids. A soft flask or hydration vest lets you sip consistently.
Electrolytes: Trails often mean more exposure to heat and sun, especially in dry climates. Make sure you're getting at least 300–600mg of sodium per hour from drink mix, salt caps, or chews.
When the pace slows, use that time to fuel, but don’t fall into the trap of only fueling only when it’s “easy.” It gets harder to eat the deeper you go — practice eating when you’re tired, breathing heavy, and sweating hard in your training.
Technical Trail 50K: Fueling in Chaos
Technical trail ultras are where race-day fueling gets a lot more tactical. The terrain can get gnarly — you’re navigating rocks, switchbacks, loose dirt, and sharp descents. You're not just running — you're balancing, climbing, and sometimes crawling.
The result? You’re working harder at lower speeds, but you often can’t eat when you need to because the terrain doesn’t let you.
Duration Expectation: Expect 6–9+ hours, even if you're well-trained. Time-on-feet becomes the challenge.
Pacing: Expect tons of variability — long climbs, slow descents, and awkward footing. Your average pace will be slower, but the effort level stays high.
What Works Best: Gels still work early in the race, but after 3–4 hours your palate gets wrecked. Alternate with salty real food: trail mix, potato chips, pretzels, jerky, rice balls, or nut butter packets.
Fuel Timing: You still need 30–60g carbs/hour — but when you eat becomes more important than what you eat. Fuel at the top of climbs or during long flats. Avoid fueling during descents where focus and balance are critical.
Hydration Strategy: Aid stations may be every 7–10 miles or more depending on the course. You should plan to carry 2–3 hours worth of fluids (and a backup plan). Mix water with electrolyte-rich drink mix or salt caps.
Common Pitfall: Not eating because the terrain is too sketchy. If you wait too long, you bonk. Learn to fuel on the move — even if it means slowing down briefly to get it down.
Like we’ve said, train for this. Practice eating on climbs, walking sections, or pauses. Have a fuel storage setup you can access one-handed and in motion — waist belt, front vest pockets, or shoulder pouches.
Mountain 50K: Altitude, Elevation, and Endurance
Mountain 50K are a totally different animal.
“At altitude, your appetite tanks — but your need for fuel increases.”
You’re often starting and racing above 6,000–10,000 feet, which affects oxygen availability, digestion, and hydration needs. On top of that, the climbs are brutal, the weather changes fast, and the time on feet is longer than most people anticipate.
If your fuel plan isn’t bulletproof, this type of race will expose it — and you.
Duration Expectation: 7–10+ hours. Time slows down at altitude — pace means less, fueling means more.
Pacing: Extremely slow in some sections — you’ll be power hiking for long stretches. Descents can be punishing and technical. You’ll be racing at a lower intensity but for a much longer duration.
What Works Best: Start with easily digestible fuel early (gels, chews, sports drink) and shift to real food the deeper you get. Your body will crave salt and substance at high elevation: PB&J, boiled potatoes, rice balls, beef jerky, electrolyte gummies.
Fuel Timing: Set a timer or reminder every 35–45 minutes to eat. At altitude, your appetite tanks — but your need for fuel increases. If you don’t eat proactively, you’ll bonk hard.
Hydration Strategy: Along with higher altitudes, cold weather masks dehydration. You may not feel like you’re sweating, but you’re losing fluid through respiration and quick-drying sweat. Plan to consume 16–24oz per hour with 300–600mg sodium per hour minimum.
Common Pitfall: Waiting too long to eat or drink because you “don’t feel hungry.” By the time you feel it, you’re already behind. Stay ahead of the hunger curve from mile one.
Altitude dulls appetite and thirst, so you have to run your nutrition like a protocol — not based on how you feel.
Aid Station Strategy by Race Type
Each race type has different support structures, and knowing what to expect is half the battle. Be sure to do your research on your specific race not just the week before, but months in advance so you can practice your nutrition strategy while training. Generally though, most races will provide something similar to the followi
Road 50K:
Aid every 2–4 miles.
You can rely on aid stations for most hydration and fuel, but always carry a small bottle with backup gels in case you miss a station.
Trail 50K:
Aid every 5–8 miles.
Carry a hydration vest or belt with at least 60–90 minutes of water and 2–3 servings of fuel.
Technical Trail 50K:
Aid every 6–10 miles.
Carry enough fuel for 2–3 hours, and expect to be self-reliant.
Bring a small first-aid item or backup salt tab stash.
Mountain 50K:
Aid may be widely spaced or impacted by weather.
Carry everything you need for 3 hours at a time.
Include extra sodium, calories, and an emergency backup fuel.
The longer and more remote the course, the less you should depend on aid stations. Build your plan around self-sufficiency and use the aid stations as bonus fuel, not your primary source.
Quick Fueling Snapshot by Race Type
ROAD | TRAIL | TECHNICAL | MOUNTAIN | |
|---|---|---|---|---|
Duration | 4–6 hours | 5–7+ hours of total race time | 6–9+ hours, even if you're well-trained. | 7–10+ hours |
Pacing | Steady, moderate pace with few breaks | Mix of hiking & running | long climbs, slow descents, and awkward footing | Varied; power hiking for long stretches |
What Works Best | Gels, drink mixes, and chews - quick digesting | Combine gels, real food, and drink mix | Start with gels, alternate with salty real food | Emphasize real food and salty snacks |
Fuel Timing | 30–60 grams carbohydrate every 30–40 minutes | 30–60g of carbs every 40–50 minutes | Fuel at the top of climbs or during long flats | Set timers for every 35-45 minutes |
Hydration Strategy | Utilize aid stations and handheld | Plan to carry your own fluids | Carry 2–3 hours worth of fluids | 16–24oz per hour with 300–600mg sodium |
Final Thoughts: Fuel the Race You Chose
Every 50K demands grit, but the demands on your gut are just as real.
The course you picked determines how much, how often, and what kind of fuel will work. Trying to run a mountain race on a road strategy is like showing up to a gunfight with a spoon.
Do your homework. Test your plan. Adapt to your race.
The right fuel, at the right time, on the right course — that’s how Dark Horses finish strong.
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